The NEC and HVAC Chapter Two

The NEC and HVAC Chapter Two - Chapter Two of the National Electrical Code (NEC) covers Wiring and Protection and starts at Branch Circuits, Feeder circuits, GFCI requirements and protection. An HVAC installer may want to pay attention to branch circuit requirements. Article 220 in Chapter two of the NEC includes calculations for branch and feeder circuits including service calculations. (Table 220.3)

The National Electrical Code (NEC) and HVAC: The Basics

The NEC and HVAC Chapter Two

Specific branch circuit requirements for HVAC can also be found in Chapter 4 Article 440 – Air Conditioning and Refrigerating Equipment Branch Circuit Conductor Sizing

Article 424 – Fixed Electric Space Heating Equipment Branch Sizing

An entire chapter on motors including feeder circuits for motors

Chapter Two of the NEC also covers basic lighting which by code is done by Volt-Amperes per square foot. (Table 220.12)

The NEC and HVAC Chapter Two

In Chapter Two of the NEC, an HVAC Technician can pay particular attention to anything in chapter two pertaining to motor loads and appliances. Before you hook up that condenser or air handler can you find the proper rating reference in the NEC for circuit size for the ampacity of the equipment you are installing?

220.82 (C) Covers heating and air conditioning loads for feeder and service load calculations.

225.30 – 225.39 makes a reference to disconnects which is applicable to HVAC equipment and HVAC equipment disconnects.

Article 230 of the NEC covers services or service entrances and not applicable to HVAC applications or HVAC equipment.

Article 240 of the NEC covers overcurrent protection and is applicable to HVAC applications and HVAC equipment. Table 240.3 (NEC 2005) references the following that is applicable to HVAC and overcurrent protection.

Air Conditioning and Refrigerating Equipment – Article 440

Appliances (possible HVAC such as window units and portable systems including air conditioners and heating) – Article 422

Article 240.5 makes a reference to the protection of cords, flexible cables, and fixture wires which are applicable to HVAC appliances that use flexible cords or flexible cables and makes a reference to Tables 400.5(A) and 400.5(B) and relates to the ampacity of the equipment served by the flexible cord or cable. Extension cords are also mentioned in this Article.

240.40 makes a reference for a disconnecting means for fuses in circuits over 150 volts which can be applied to HVAC equipment since a lot of HVAC equipment is over 150 volts. Article 240.50 makes a general reference to fuses and the allowable use of fuses. Read that article to see if this applies to your specific HVAC application.

The NEC and HVAC Chapter Two – Article 250 – Grounding and Bonding

Grounding and Bonding is applicable to HVAC and HVAC equipment and is very important to any electrical circuit in most residential and commercial HVAC installation. What happens if there is a dead short in a compressor and the homeowner touches the condenser if no ground exists? Current will pass through the homeowner and to the ground where he or she is standing. Electricity takes the path of least resistance and the homeowner made the circuit from the short in the compressor to ground. The subject of grounding and bonding is very important to understand so I recommend you consult a professional electrician if there are any questions about the circuit(s) being used are properly grounded and/or bonded. This includes the circuit wire size is appropriate and/or the path to ground is effective.

The NEC and HVAC Chapter Two – Article 280 – Surge Arresters

This is applicable to commercial applications and government retrofit and new construction jobs. Surge arresters may be something to consider for residential and commercial applications especially for solid-state equipment that utilizes electronics and is highly susceptible to lightning strikes or other natural or unnatural surges. Whether solid state electronics are used or not is good to protect all equipment including HVAC equipment from surges.

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HVAC Random Tip Box

HVAC Tip - Did you know the human body produces approximately 250 BTU/h when sleeping? Here is a basic list of the approximate BTU/h produced by the human body for various activities:

Watching Television - 400 BTU/h (any sedentary activity)

Cleaning the house - 700 BTU/h (moderate activity)

Mowing the Grass w/push mower - 1800 BTU/h (heavy activity)

Running a marathon - 2400 BTU/h (extreme activity)

The number of people occupying a dwelling or space is a consideration in the load calculation for sizing air conditioning systems simply because humans do give off heat. BTW, the Matrix over blew the numbers. In the movie Morpheus states humans give off over 25,000 BTU's. Only the author of this website is that hot..............))))))

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